38 PRACTICAL MEASUREMENTS 



subtract the weight of the pail. Now divide the weight of 

 the sand by the weight of the water. The quotient is called 

 the specific gravity. 



If the substance whose specific gravity is to be found is 

 of an irregular shape, for instance, a piece of iron, 

 weigh it. Then place it in a pailful of water. Some of 

 the water, an amount equal to the bulk of the substance, 

 will run out. Weigh the water that runs out, and divide 

 the weight of the substance by the weight of the water 

 that runs out. The quotient will be the specific gravity 

 of the substance. 



43. Rule. To find the specific gravity of a substance, divide 

 its weight by the weight of an equal volume of water. 



EXERCISE 



1. A cubic foot of zinc weighs 437.5 lb., and a cubic 

 foot of water weighs 62.5 lb. What is the specific gravity 

 of the zinc ? 



2. A cubic foot of lead weighs 712.5 lb., and a cubic 

 foot of water, 62.5 lb. What is the specific gravity of 

 the lead? 



3. The specific gravity of cast iron is 7.4. What is the 

 weight of a bar 2 ft. long, 9 in. wide, and 8 in. thick ? 



4. Find the specific gravity of a pailful of gravel, and 

 estimate the weight of a load of gravel in a bed 9 ft. long, 

 3 ft. wide, and 12 in. deep. 



5. A flatboat 40 ft. long and 12 ft. wide sinks 2^- in. when 

 a team drawing a load of wheat is driven upon it. What 

 is the combined weight of the team, wagon, and load .? 



6. To what depth will 400 bu. of wheat sink a flatboat 

 60 ft. long and 18 ft. wide ? 



